Portable power cable



June 16,1942. J. J. MoRRlsoN '2,286,826

' PORTABLE POWER CABLE I Filed Aug. l,- 1940 COA/00670@ CoA/00670,@

.Jb/W55 J Magg/50N,

Patented June 16, 1942 PORTABLE POWER CABLE James J. Morrison,Worcester, Mass., assignor to The American Steel `and Wire Company ofNew l Jersey, a corporation oi' New Jersey Application August 1, 1940,Serial No. 349,192

2 Claims.

This is a continuation-impart of my application liled September 29, 1936and bearing Serial No. 103,193. The invention is a portable power cableusing rubber fillers yet having a exibility comparable to that obtainedby the use of jute or other brous llers. y

A portable cable is understood by those skill'ed in the art to mean athree or four conductor cable used in mines, quarries, etc. to powerelectric shovels, dredges, cranes and similar electric equipment@ Itworks under high potential, which sometimes exceeds 4500 volts, it mustbe flexible to permit its continual reeling and unreeling on and offdrums, and it must be comparatively light in weight yet sufficientlytough and durable to withstand the severest usage. It is dragged overrocks and rough ground, exposed to the elements at all seasons, yetm'ust continue to give uninterrupted service.

The customary way to make a portable power cable is with stranded copperconductors which are tinned and covered by rubber insulation, theinterstices between the rubber insulations being provided with fillersto smooth out the cable contour and a vulcanized rubber jacket or beltbeing used to close this assembly of elements. Ground wires are usuallylaid in the interstices between the rubber insulations and the lattermay carry electrostatic shielding if the cable is to work at extremelyhigh potentials, such as over 4500 volts. The iiller used to smooth thecontour of the cable is jute or other fibrous material.

Now it has always been considered desirable to substitute rubber fillersfor the" jute or other brous llers, the latter being cojectionable inthat they do not provide the firmness and elasticity or the greaterresistance to impact or crushing weight alforded by rubber, they beingsubject to the further objection that should the jacket of the cable becut through, water, oil, etc., which might enter, migrates along thecable so as to result in a baggy effect, and, possibly, cause rotting ofthe llers.

However, the incorporation of rubber llers in a portable power cablepresents a problem in that the vulcanized rubber jacket overall pressesthe llers`against th'e insulated conductors so as to prevent theirmoving relative the fillers during the flexing and twisting to which aportable power cable is subjected during service, and the normalpractice of vulcanizing rubber. fillers after assembly caused them toadhere to the rubber conductor insulations so as to increase thetrouble. Ef-

forts have been made to preform and prevulcanize the rubber llers, tocoat the insulated conductors with lubricating material, such as talcum,graphite, etc., all without any definite gain in flexibility althoughwith a great increase in cost. Prior to the present invention theproblem of providing a portable power cable with` rubber fillersremained unsolved, the fillers used being all jute or other material.

According to the present invention, the above problem is solved byplacing a layer of regenerated cellulose or cellulose acetate aroundeach of the rubber insulated conductors so as to provide antifrictionsurfaces for aiding the required sliding of the rubber insulatedconductors relative the rubber llers. If shielding is used, theantifriction layer may be placed either between the rubber insulationand the shielding or between the shielding and the rubber fillers. One,two or more antifriction layers may be used in any event, dueconsideration being had for cable enlargement, two layers producing amore flexible product than one layer. In the commercial form of theinvention the layer is now formed by winding thin cellulose acetate tapeover the rubber insulation with the convolution' edges slightlyoverlapping.

It has been found that either regenerated cel- 'lulose, such as thecommercially available Oellophane, or cellulose acetate, are bothpractically unaffected by the heat necessary to effect vulcanization ofthe rubber fillers and the rubber jacket, so the fillers can beassembled and vulcanized without sticking to any of the insulatedconductor assemblies which must slide relative the fillers. Furthermore,these materials are not acted upon by the chemical ingredients in rubbercompounds lor other types of insulation, and they are practicallyimpervious to oil, asphalt, or other materials commonly used in themanufacture of electric cable. Furthermore, due to their inherentcharacteristics they can be provided with different colors so as to aidin conductor identiiicationduring cable insulation work.

In addition to the two materials specifically mentioned, it isconceivable'that other materials may be used providing they areresistant to the heat necessary to effect vulcanization of the flllersand jacket, are resistant to the chemicals commonly encountered in cableconstructions and present glassy, slippery surfaces to the relativelysliding cable elements. This is mentioned because of the rapid progressnow being made in materials having the characteristics of regeneratedcellulose and cellulose acetate, but it is to be understood that oiledor calendered paper and many other materials may prove unsuitable forthe use now under discussion, since the material used must have thecharacteristics mentioned.

The accompanying drawing illustrates the commercialized form of theinvention by way of providing the required specific example of the same.Since this drawing carries legends indicating the various elements ofthe cable, it is unnecessary to further describe the same in view ofwhat has already been said. However, before closing, it

should be understood that the rubber components are actually rubbercompound and that they may be made of artificial rubber, the term rubberbeing used to cover either of these.

I claim:

l. An electric cable of the portable type including a plurality ofconductors, at least one layer of material immovably xed over each ofsaid conductors, rubber fillers for smoothing the cable contour, ajacket covering all said elements and pressing them toward one another,and a 20 cellulose acetate.

layer of regenerated cellulose or cellulose acetate heat necessary toeffect vulcanization of saidv jacket and to chemicals commonlyencountered in cable constructions and presenting slip'pery surfaces tosaid insulation and said llers, said surfaces having the physicalcharacteristics. of surfaces provided by regenerated cellulose or JAMESJ. MORRISON.

